Figure 8-3.-Plastic pipe fittings.PLASTIC PIPE.— Plastic pipe has seenextensive use in current Navy construction.Available in different lengths and sizes, it is lighterthan steel or copper and requires no special toolsto install. Plastic pipe has several advantages overmetal pipe: it is flexible; it has superior resistanceto rupture from freezing; it has completeresistance to corrosion; and, in addition, it canbe installed aboveground or belowground.One of the most versatile plastic and polyvinylresin pipes is the polyvinyl chloride (PVC). PVCpipes are made of tough, strong thermoplasticmaterial that has an excellent combination ofphysical and chemical properties. Its chemicalresistance and design strength make it an excellentmaterial for application in various mechanicalsystems. Sometimes polyvinyl chloride is furtherchlorinated to obtain a stiffer design, a higherlevel of impact resistance, and a greater resistanceto extremes of temperature. A CPVC pipe (achlorinated blend of PVC) can be used not onlyin cold-water systems, but also in hot-watersystems with temperatures up to 210°F.Economy and ease of installation make plasticpipe popular for use in either water distributionand supply systems or sewer drainage systems.GALVANIZED PIPE.— Galvanized pipe iscommonly used for the water distributing pipesinside a building to supply hot and cold water to8-3the fixtures. This type of pipe is manufacturedin 21-ft lengths. It is GALVANIZED (coated withzinc) both inside and outside at the factory toresist corrosion. Pipe sizes are based on nominalINSIDE diameters. Inside diameters vary with thethickness of the pipe. Outside diameters remainconstant so that pipe can be threaded forstandard fittings.CAST-IRON WATER PIPE.— Cast-ironpipe, sometimes called cast-iron pressure pipe, isused for water mains and frequently for servicepipe up to a building. Unlike cast-iron soil pipe,cast-iron water pipe is manufactured in 20-ftlengths rather than 5-ft lengths. Besides bell-and-spigot joints, cast-iron water pipes and fittings aremade with either flanged, mechanical, or screwedjoints. The screwed joints are used only on small-diameter pipe.FittingsFittings vary according to the type of pipingmaterial used. The major types commonly usedin water service include elbows, tees, unions,couplings, caps, plugs, nipples, reducers, andadapters. Some typical copper pipe fittings areshown in figure 8-2. Plastic pipe fittings (fig. 8-3)that are similar in appearance to those used withmetal piping are available. Some plastic pipes can
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